Scientists sound the alarm on ocean acidification, but who’s listening?

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Covering science in the modern day, your reading list leads to a number of frequently recurring questions. One of the most intractable is: how many apocalypses (apocalii?) can the human race address at one time? Even countries that have explicitly pledged to confront climate change often struggle to make the large-scale adjustments we’d need to actually affect anything; what if I told you there was a second, large-scale ecological disaster looming, one with similar causes but a totally different list of possible consequences? How much attention and effort would we realistically have left to give to such a problem, if one existed?

That issue might well be ocean acidification, especially given some recent statements from Britain’s science chief and numerous high-ranking oceanographers. Ocean acidification is both more and less concrete than climate change, in that there is even less question as to whether the basic change is occurring and will continue to occur in the future.

It’s a lot easier to look back into geological time through the lens of acidity than temperature, and concrete data shows that the world’s oceans have increased by roughly 25% since the industrial revolution – just 0.1 pH units, but remember it’s on a log scale. By contrast, other research shows that it has steadily decreased for about the last 20 million years, and with the current level of acidification we’ll reach that 20-million-year high again by 2100.

Estimated change in sea water pH caused by human created CO2 between the 1700s and the 1990s, from the Global Ocean Data Analysis Project (GLODAP) and the World Ocean Atlas.

But, is that so bad? Our primate ancestors seem to have come through that period after all, and didn’t we turn out OK? Well, there are two problems. One: while the actual pH is not unprecedented on the geological scale, its rate of change absolutely is; in just 350 years (ending in 2100) we might completely rebound from a pH decrease that took 20 million years to occur int he first place. The last time the earth’s oceans changed pH that dramatically was about 65 million years ago — if that number sounds familiar, it’s because that’s around when a planet-killing meteor (very, very probably) struck the earth, killed off the dinosaurs, and changed the world forever.

CO2 and water combine to make carbonic acid.

Ocean pH seems to be changing primarily because of atmospheric level of CO2, which dissolved at the surface of the ocean and forms carbonic acid. So, if the oceans are definitely acidifying at an unprecedented rate, what effect might that have? Well, about 55 million years ago there was a huge and swift change in ocean temperature, about 6 degrees over just a few thousand years, and there was no huge extinction of surface dwelling organisms — but a huge extinction at the bottom of the ocean. Deep ocean creatures enjoy a much more stable environment, and are far less able to adapt to changes in their climate than land-based species.

Change in pH could have much more far-reaching effects than temperature though. One of the main proximate victims would be the world’s coral reefs, which are responsible not just for holding a huge portion of the world’s biodiversity, but for maintaining enormous ecosystems and thus feeding huge numbers of people. There are whole islands that would not exist without coral to break ocean waves. Sea urchins, starfish, and other “echinoderms” are also highly vulnerable, which could be an even bigger issue; these animals occupy a “keystone” position in their ecosystems, and are often the only thing keeping rabid species of algae from coating huge areas of the ocean floor and choking complex ecosystems out of existence.

Not to sound like every second-grade teacher ever, but food webs are extremely delicate and interdependent. There’s no way to imagine that we could institute a large-scale extinction in the oceans and not feel its effects on land. There’s no way to tell which species might be affected, from important marine food species to birds that live off the oceans to land plants that live in coastal areas, and the animals they support. The effects of a drastic pH drop could easily reach far inland, even on the largest continents.

Fighting ocean acidification, however, might just end up being easier than global temperature change, that it doesn’t seem like it will enter a destructive feedback loop in which lowering pH causes further acidification, and so on. Also, by virtue of being water, it’s theoretically easier to directly affect the composition of the oceans than the atmosphere. Still, ocean acidification is a tough subject; the researchers who cover this topic talk with a sort of restrained panic, seemingly not wanting to sound too, too much like their climatologist colleagues.

Maybe it’s time for them to start — whether or not they’re likely to succeed.